The present invention relates generally to automation of pulsed laser deposition.
In PLD operation, the deposition is made by energizing a material to be deposited into a high energy state by high energy laser light, after ultraviolet light. The material is typically in an ultrahigh vacuum environment, and is in solid state. The laser beam is generated by an eximer laser and focused on a target of material that is to be deposited. The laser beam is pulsed, and focused on the surface of the target material, so that target material is liberated into a high energy state, and deposits onto the surface to be coated. This complex equipment requires that continuous monitoring be done of not only the high energy laser device, but also the vacuum environment where the material to be deposited is contained.
The laser beam is not fixed in position of the target, but is often moved across the surface of the target so that excessive target damage will not occur. The laser beam is moved by a motorized mirror. The mirror must be calibrated so that the focused laser beam impinges on the target surface only, and not the target holder. Setup of the PLD system requires that the laser beam be calibrated so that the raster pattern will utilize as much target surface as possible, yet not impinge on the target holder. Each time the laser beam is focused, a re-calibration of the target edges is necessary. This process often requires the operator to be in the room, to look at the laser beam as it impinges on the target surface, and make corrections to the position of the beam as it moves across the target. The risk of operator exposure to ultraviolet light is high when doing the calibration. Remote operation removes this risk.
The proper operation of a PLD system requires that the ultra-high vacuum be sound, that the laser beam is focused onto the target correctly, and that the laser be functioning correctly. Maintaining these parameters during a PLD deposition requires the operator to monitor many system gages and indicators. Typically, these indicators are centrally located with the laser and ultrahigh vacuum apparatus. The operator must simultaneously record several values, while conducting a deposition.
The following publication items are of interest with respect to the present invention.
S. J. P. Laube and E. F. Stark, "Feedback Control of Pulsed Laser Deposition Processes", AIP Conf. Proceedings 288, Laser Ablation: Mechanisms and Applications-II, Second International Conference, Knoxville, Tenn., April 1993. pp.242-247.
E. F. Stark and S. J. P. Laube, "Self Directed Control of Pulsed Laser Deposition", ASM Journal of Materials Engineering and Performance, Vol. 2, No. 5, October, 1993, pp. 721-725 [cited as JMEPEG (1993)2:721-726], ASM International.RTM., Matertials Park, Ohio 44073-0002.
S. J. P. Laube and E. F. Stark, "Artificial Intelligence in Process Control of Pulsed Laser Deposition", AIRTC'94 Symposium on Artificial Intelligence in Real Time Control (Preprints), Valencia, 3-5 Oct. 1994.
The above three papers authored by applicants are closely related to the invention.
Other papers of interest include:
J. Cheung, J. Horowitz, "Pulsed Laser Deposition History and Laser-Target Interactions" MRS Bulletin, vol. 17, No. 2 (February 1992), pp 30-36.
R. K. Singh and J. Narayan, "Pulsed-Laser Evaporation Technique for Deposition of Thin Films: Physics and Theoretical Model", Physical Review B, The American Physical Society, Vol. 41, No. 13, May 1990.
P. S. P. Wei, R. B. Hall, and W. E. Maher, "Study of Laser-Supported detonation Waves by Time-Resolved Spectroscopy", The Journal of Chemical Physics, Vol. 59, No. 7, 1 Oct. 1973, pp. 3692-3700.
D. B. Geohegan, "Physics and Diagnostics of Laser Ablation Plume Propagation for High-T.sub.c Superconductor Film Growth", Solid State Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tenn. 37831-6056, submitted for the International Conference on Metallurgical Coatings and Thin Films, ICMCTF-92, San Diego, Calif., Apr. 6-10, 1992.
D. B. Geohegan, "Effects of Ambient Background Gases on YBCO Plume Propagation Under Film Growth Conditions: Spectroscopic, Ion Probe, and Fast Photographic Studies", Solid State Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tenn. 37831-6056, submitted for the E-MRS Summer School on Laser Ablation of Electronic Materials: Basic Mechanisms and Applications, Carcans-Maubuisson, France, September, 1991.
D. B. Chrisey and A. Inam, "Pulsed Laser Deposition of High T.sub.c Superconducting Thin Films for Electronic Device Applications", MRS Bulletin, February 1992.
S. R. Foltyn, R. E. Muenchausen, R. C. Estler, E. Peterson, W. B. Hutchinson, K. C. Ott, N. S. Hubbard, R. C. Dye, X. D. Wu, "Influence of Beam and Target Properties on the Excimer Laser Deposition of YBa.sub.2 Cu.sub.3 O.sub.7-x Thin Films", Los Alamos National Laboratory, Los Alamos, N.M. 87545, Materials Research Society Symp. Proc. Vol. 191, 1990, pp 205-209.
N. H. Cheung, Q. Y. Ying, J. P. Zheng, and H. S. Kwok, "Time-Resolved Resonant Absorption Study of 532-nm Laser-Generated Plumes Over YBa.sub.2 Cu.sub.3 O.sub.7 Targets", J. Appl. Phys. 69(9), 1 May 1991, American Institute of Physics, pp. 6349-6354.
T. Venkatesan, X. D. Wu, A. Inam, and J. B. Wachtman, "Observation of Two Distinct Components During Pulsed Laser Deposition of High T.sub.c Superconductor Films", Appl. Phys. Lett 52 (14), 4 Apr. 1988, American Institute of Physics, pp 1193-1195.
A. Gupta, B. Braren, K. G. Casey, B. W. Hussey, and R. Kelly, "Direct Imaging of the Fragments Produced During Excimer Laser Ablation of YBa.sub.2 Cu.sub.3 O.sub.7-.delta. ", 1991.
G. Koren, A. Gupta, R. J. Baseman, M. I. Lutwyche, and R. B. Laibowitz, "Laser Wavelength Dependent Properties of YBa.sub.2 Cu.sub.3 O.sub.7-.delta. Thin Films Deposited by Laser Ablation", Appl. Phys. Lett 55 (23), 4 Dec. 1989, American Institute of Physics, pp 2450-2452.
A Inam, and X. D. Wu, "Pulsed Laser Etching of High T.sub.c Superconductor Films", Appl. Phys. Lett 51 (14), 5 Oct. 1987, American Institute of Physics, pp 1112-1114.
E. G. Scott, S. T. Davey, M. A. G. Halliwell, and G. J. Davies, "Improvements to and Characterization of GaInAs Heterointerfaces Grown by Molecular-Beam Epitaxy", J. VAc. Sci. technol. B 6, Mar/Apr 1988, American Vacuum Society, pp. 603-605.
C. E. Otis, and R. W. Dreyfus, "Laser Ablation of YBa.sub.2 Cu.sub.3 O.sub.7-.delta. as Probed by Laer-Induced Fluorescence Spectroscopy", Physical Review Letters, 7 Oct. 1991, The American Physical Society, pp. 2102-2105.
T. Spalvins, "Lubrication with Sputtered MoS.sub.2 Films: Principles, Operation, and Limitations", ASM Journal of Materials Engineering and Performance, Vol. 1, No. 3, June, 1992, pp. 347-351 [cited as JMEPEG (1992)1:347-352], ASM International.RTM..
P. T. Murray, V. J. Dyhouse, L. Grazulis, and D. R. Thomas, "Dynamics of MoS.sub.2 Photoablation", Mat. Res. Symp. Proc. Vol. 201, 1991, Materials research Society, pp. 513-518.